If you have 20% downside protection in a nearly even odds game, you can figure out the optimal strategy. Also, he was betting $100k a hand, so he didn't have to play too many hands before deciding to stop as a winner or take his 20% loss rebate. (If you have the 20% loss protection, the optimal strategy is to bet big.)

For example, his downside protection was 20% of a loss of at least $500k. If he was at -400k, he had no reason to quit; he should keep playing until he was ahead or at -500k.

Also, casinos previously negotiated 20% loss rebates on a LIFETIME basis. He negotiated the 20% loss rebate on a PER-TRIP basic, correctly pointing out that if he was ahead at a casino, he had no reason to return if another casino also offered the rebate.

The lt;dr summary is: He didn't cheat or count cards. The 20% loss rebate combined with blackjack being a nearly even game gave him an edge.

You could do the same thing at craps. At craps, there's an obscure rule that lets you make a bet at true odds after establishing a point, sometimes for 10x or more of your original bet. If you're playing at a place that offers the 10x backup bet and the 20% loss rebate, you could do the same thing at craps.